Antibodies and Complements - Quan Flashcards
What are the 4 important features of antibodies?
- bind a variety of antigenic structures
- Exquisite discrimination of similar antigens
- Bind antigen with great strength
- Recognize antigen in its native form.
What is the Overall mission of antibodies?
Neutralize target antigen
__________ is tagging microbial organism or infected cells for phagocytosis.
opsonization
______ recruit complement system to destroy microbial organisms or infected cells.
Complement fixation
__________ bind toxins in the blood and tissue to facilitate the removal of the toxins.
Direct neutralization
What is the major Immunoglobulin (Ig) in serum? What does it do?
G (IgG) = 70-75% Provides; neonatal immunity plays role in immunological memory IgG represents the basic structure of all Ig's
Describe IgD….
Less than 1% of circulating Ig’s
A major component of B cell surface Ig
Also called b-cell receptor
Describe IgE….
- Very scarce in serum
- Found of the surface of basophils
- Important for killing large parasites
- Contributes to allergic reaction
Describe IgA…
- Is seceted into the saliva
- The receptor for IgA transports IgA across mucosal epithelium
- IgA usually assembled as a Dimer.
Describe IgM…
- Around 10% of total Ig’s
- A pentamer of basic Ig structure
- Can serve as a B cell receptor
- The first secreted Ab in the response to the initial antigenic challenge.
_____ complement is the Central component
C3
______ - ______ complements are the late complements.
C5-C9
What is the Complement family?
30 serum molecules that make of 10% of serum proteins.
What does the complement family do?
A major defense system of the body that contributes to: Control of inflammation Chemotaxis Clearance of immune complexes cellular activation antimicrobial defense
_____________ are the active complements.
Fragments of the complement molecules.
How does complement activation occur?
Active site of complement is “Unmasked” by proteolytic cleavage, resulting in the exposure of the active site.
Many complement components are ________.
Proenzymes
The 3 principle functions of the complement system are what?
- Opsonization & cell activation
- Chemotaxis = small fragments of comp. form a concentration gradient to stimulate movement of immune cells to infection site.
- Lysis of target cells = Activation make (MAC) which inserts into lipid bilayer, makes holes an causes lysis.
Activation of complement system leads to _________ which causes ________.
- Formation of MAC
- causes lysis of microbe
What are classic pathway activators?
Antibody-antigen complexes containing IgM or lg.-3
What are lectin pathway activators?
Terminal mannose groups
What are alternative pathway activators?
Microbial cell walls
Which pathway activators are found on microbial surface?
Lectin & Alternative
Know the summary of early stage activation of the alternative pathway….9 steps.
Spontaneous cleavage of C3 generate C3a & C3b—>C3b in fluid deactivated by hydrolysis—>C3b covalently bonds to cell surface–>Self surface bound C3b binds to factor H–>C3bH deactivated by factor I—>C3b bound to the surface of microbes binds to factor B–>C3bB is cleaved by factor D to generate C3bBb—>C3bBb is the alternative pathway C3 convertase.
*C3bBb catalyze significant amount of C3 Cleavage.
___ is the adapter for the Classic pathway.
C1
During the selective engagement by the classical pathway, _________ do not engage C1
Free antibody
During selective engagement by the classical pathway, tissue bound antibody activates C1 generating what?
C1qr2s2
What are the 3 steps of the Classical pathway?
Activated C1 cleave c2 and c4 to form C4b2a—->C4b2a is the classical c3 Convertase——> C4b2q3b is the classical C5 convertase.
_____ is required for the invitation of MAC.
C5b
